As portable devices or appliances become widely used, compactness and light weight of product become key issues along with a faster processing speed under current communication environments requiring faster transmissions of large capacity data. The use of low-voltage and low-power type semiconductors increases with the aid of highly integrated semiconductor, high speed switching devices for fast processing and portable devices and appliances.
Subsequently, such trend gives rise to developing and designing a circuit that is highly sensitive to an instant pulse and a transient voltage, with the result that downing of integrated circuits (IC) occur. It becomes necessary to use an instant pulse filter in preventing such IC downing.
The instant pulse filter is generally applied to a device requiring a high speed data transmission such as a cellular phone, a palmtop computer, a USB 2.0 controller, a HD TV, a set top box, antenna, RF circuits and etc. As high density data integration and high speed processing increasingly become a necessity, more attention is being paid to properly dealing with instant pulses.
As shown in FIG. 1, the instant pulses have been conventionally dealt with by using a polymer composite material prepared by mixing a conductive powder 40 to a polymer resin 30. An internal electrode 20 is formed in an epoxy substrate 10, and a polymer composite material is filled between the internal electrodes 20, and an external electrode 50 is formed on both sides of the same.
As shown therein, a polymer composite material is prepared so as to obtain a low discharge voltage on an upper side of the epoxy substrate 10. The polymer composite material can be applied as a discharge electrode in such a manner that a metallic conductive powder 40 is dispersed in a polymer resin 30, and an instant pulse path 60 is formed with the aid of the conductive powder 40. The polymer composite material is known to have many advantages—a low electrostatic capacity, a low leakage current and etc.
Another conventional art uses a ZnO laminated Varister in which ZnO is a voltage variable type resistant material.
The conventional instant pulse filter works like this: when polymer is used, it focuses on an electron tunneling by means of an electric field between neighboring conductive particles, and when laminated Varister is used, it is also based on electron tunneling by means of electric fields of short key barriers formed between ZnO grain and grain boundary.
The conventional technology using polymer does not properly work because a polymer resin with conductive metallic powder is weak to excessive instant pulse. Namely, as it becomes carbonized with resultant decrease of resistance, leakage occurs in grounding path with respect to a high speed digital signal, leading to a distortion and loss of data, with the result that digital signals are leaked to grounds instead of being normally transmitted, thus impeding the operation of the system.
When polymer is used, the thickness of energy barrier is not uniform due to a random distribution of conductive particles, so the nonlinearity of resistance with respect to the voltage of device is bad, and instant pulse energy capability is poor due to the characteristic that current tends to better flow toward a barrier having a lower energy when current flows via a voltage variable type resistance material (the entire portions of a voltage variable type resistance material between electrodes cannot be used as a current path). When a current path is formed on thin barriers, and a lot of current flow via the current path, thereby shortening the product life.
When laminated Varister is used, it has nonlinearity and high instant pulse absorption capacity, but a data distortion might occur due to a large electrostatic capacity when transmitting data at a high speed.
Neither polymer nor ZnO laminated Varister lend themselves to adjusting the dimensions of energy barriers of micro structures.